Summer officially began early this morning: the baseball strike is over.

The longest strike in sports history began 50 days ago in late spring and forced the cancellation of 706 games and 35 percent of the regular major-league season. It ended officially with the formal announcement of a settlement at 5:45 a.m. today, at the oint of the season when the muddled pennant races of August usually start and shortly before the owners' strike insurance was due to run out Wednesday.

Play will begin Sunday, Aug, 9, with the All-Star Game in Cleveland. Regular-season play will be resumed the next day with regularly scheduled games, including the Kansas City Royals visiting Baltimore to play the Orioles at 7:30 p.m. Players will begin working out Saturday.

The executive board of the Major League Baseball Players Association, the players' union, will meet in Chicago Saturday to review and probably recommend ratification of the agreement. [More details, Page D1.]

An owners' meeting has been scheduled for Tuesday in Chicago, at which, it is expected, the format for the rest of the season will be discussed. wThe agrement provides the owners with the option of playing the remainder of the season and the playoffs as they ordinarily would or using a split-season playoff instead.

The strike was traumatic for everyone involved, including the American public, which learned just how much of a grip baseball has on its consciousness. "I think we own them all an apology," said Lenny Randle, the Seattle Mariner third baseman.

For 49 days, negotiators and fans debated the merits of free-agent compensation, the issue the provoked the strike. The tentative agreement provides teams compensation in the form of a professional player in some cases, and additional amateur compensation in others. Previously, the only form of free-agent compensation was an amateur draft pick.

The agreement provides the players association with the pooled compensation arrangement it had sought to protect its members' bargaining power and marketability.

As part of the agreement, the players received full major league service credit for the time they were on strike, a demand they had said was "etched in stone," in exchange for dropping the unfair labor practice suit they had brought against the owners with the National Relations Board. They also agreed to a one-year extension of the Basic Agreement, scheduled to expire at the end of the 1983 season.

"The most important thing is that we got another year of peace," said Edward Bennett Williams, owner of the Orioles. "Never again. It must never happen again."

Roy Eisenhardt, the president of the Oakland A's, agreed. "What has to happen is that we have to assess why this happened without emotion and venom. We need the additional time to reorient our thinking and our structure so these earthquakes don't have to occur again."

"It is clear that both sides lost," said Jerry Reinsdorf, co-owner of the Chicago White Sox. "The strike was senseless."

The strike, which both sides continually insisted was unnecessary, will leave scars. There already is talk that officials on both sides will be different the next time around. Management sources predict both Commissioner Bowie Kuhn and the owners' chief negotiator, Ray Grebey, will be replaced. Marvin Miller, the executive director of the players association who has often spoken of retiring, said, "I have a strong feeling I won't stay around for future negotiations."

The additional year on the contract, Miller said, would make that transition easier for everyone.

The strike may represent the end of an era in baseball's 100-year labor war. New owners, such as Eddie Chiles of the Texas Rangers, may reflect a new attitude toward the "new" players.

Chiles said early today he was proud of those players for the dignity with which they handled themselves during the strike.

"They hung thight, they hung tough, they're made of strong stuff," Chiles said. "You gotta be proud of them. If we run our business right, (putting) the higher class people on the field, the better the game is going to be. If we know they hang tough, that they know what they want and will do what is right to get what they want, then the owners will be obliged to work on an equal basis with them.

"I'm not saying, 'Give 'em everything,' like a spoiled child. But give them what is fair and equitable and what they need to have."

And, said Eisenhardt, another of the new owners, "Give it without resentment."

The players, who regarded this strike as a "take-back" negotiation, in which they had to give back some of the rights they have had since 1976, were not jubilant about the terms of the settlement.

Dick moss, a consulting attorney for the players association, said he expected the agreement to be ratified, although not unanimously.

Mark Belanger, the player representative of the Orioles, said, "It's a good agreement. I don't consider it great. But you have to weigh it against the real possibility of the loss of the 1981 season and the irreparable damage to the game in 1982."

When the strike began on June 12, the owners were still asking for compensation that, in many cases, would have given a team losing a free agent the 16th man off the other club's roster. On June 7, the players offered a proposal for pooled compensation that stipulated for the first time that each team would designate one man off its 40-man roster for the pool.

The proposal that the two sides settled on provides a pool. It allows the team losing a ranking free agent to receive, at the most, the 25th man off another team's roster.

Ranking free agents are defined as those in the top 30 percent of performance statistics based on a two-year average (those with 12 or more years in the majors and those who have been free agents are excluded fron the rankings). Players in the top 20 percent of the statistics are considered Type A, or premium, free agents, the signing of whom may require professional compensation.

The number of Type A free agents requiring professional compensation is determined by the number of teams contributing to the pool each year.

According to the agreement, as many as five teams each year may elect not to participate in the pool. Those clubs may not sign or select a Type A free agent for three consecutive years.

If all 26 clubs participate in the pool in 1981, there will be a maximum of eight Type A free agents. If only 21 teams participate, there will be a maximum of seven. At not ime during the life of the agreement can there be more than nine Type A free agents in any one year.

A team that p articipates in the pool but does not sign a Type A free agent will be able to protect 26 men in its organization. All others go into the pool. A club signing a free agent will be able to protect 24 men in its organization, with all others going into the pool. However, no club can lose more than one player a year as compensation.

If a team signs no type A free agents, it can lose only one player as compensation over a three-year period. If a team signs, for example, three Type A free agents in 1981, it can lose one player a year off its 24-man protected list over the three-year period.

Free agents participating in the draft may be selected by any number of clubs. Previously, a free agent could be selected by only 13 teams.

The team losing the player will receive as compensation $150,000 from a fund created by equazl contributions from each club. However, a team can receive that payment only once over the three-year period.

The agreement on the compensation issue, which had proved so intractable for so long, "provides us with what we wanted, and what they needed," according to Grebey.

Once the compensation issue was resolved, the only thing that remained was full service credit. Tghe negotiatoars did what baseball always does: they traded for it. The players gave up their NLRB suit and agreed to a one-year extension on the Basic Agreement, in exchange for full service credit, a suggestion that had been made several weeks ago by Williams.

As part of the deal, the pension benefits, which are tied to the yearly network television contract, will be applied retroactively to the extended year of the contract.

The clubs must decide whether to use the split-season system by Aug. 9. If the split season is used, the winner of the prestrike and poststrike seasons will meet in a best three-of-five game playoff. If a club wins both portions of the split season, Grebey said, it will probably get a bye.

Players said he would probably support the split-season concept to revive the interest of the fans, although, he said, it is not to the advantage of the Orioles bacause they are in the thick of the race.

Eisenhardt said, "I like it for two reasons. The first is obvious (the A's are in first place in the West Division) and the second is that it gives the rest of the season credibility."